The Mysterious Schoolmaster

Book excerpt: Why should Mr. Engman, the physics teacher, enter the school building at night by a basement door? Why should he and a mechanic meet secretly at odd times and places? Cecilia and Michael, who stumble on these fats by sheer accident, suspect that military espionage may be involved, and when Michael follows, the mechanic his worst suspicions are confirmed--and there the boy suddenly finds himself in deadly peril. (Publisher).